a 70 meter rope for 89$
You mean This one?
Obviously not for what we'd call climbing, but does it actually have a related use somewhere? EDIT, yeah, that's really misleading - all the 5-star reviews are using it to hang garden swings :)
There are plenty of legit brands. Some were unknown to me, probably for the reason you mentioned.
You can check the UIAA database to see if a company has a current certification for the item you're searching. https://www.theuiaa.org/safety/safety-standards/certified-equipment/
Aside from very real concerns about counterfeit gear for the comingling reasons mentioned above, I don't want to support a company that continues dangerous practices like listing garbage like this alongside legitimate products.
Ultimately it's up to the climber to know what is an appropriate piece of gear for each situation. But continuing to keep these items listed in the "climbing" section and showing photos of them being used in climbing situations may legitimize them in the eyes of someone new. And someone is going to get seriously injured or killed. Based on some of the photos in reviews on similar products, there are definitely people using these "ropes" as part of their safety system.
Edit:Here's some more info from a thread I started in /r/climbing about it awhile ago.